Hi Neil,
The short answer to that question is - no.
I've not come across any documentation that specifically permits or forbids the use of longer (than 3mtr) power supply cables on any device, IFUs/IFMs included.
I can say though that it's not uncommon for users to require leads longer than 3mtrs where I work, given the practicalities of plugging in a variety of equipment in various clinical spaces.